Offset error if the first item in an admin menu is a separator

[phill_brown]

There are a few ways you can get to this error, but the easiest way with the default install is:

add_action( 'admin_menu', create_function( '', 'unset( $GLOBALS[\'menu\'][2] );' ) );

I originally came across the error assigning the manage_sites capability to a non super admin role. If you do the same and visit /wp-admin/network/sites.php - you'll see the same error.

If this fix is approved, it raises another minor issue with the network page. There's now an unnecessary separator at the top of the menu. The second patch (network-menu) assigns the same capability requirement to the separator as the dashboard.

[phill_brown]

Fixes offset error if separator is first in the admin menu

[phill_brown]

Fixes UI issue showing a non-required separator

[SergeyBiryukov]

Confirmed the notice. The fix looks sane to me.

Refreshed as a single patch with proper file paths in 23182.patch​.

[SergeyBiryukov]

Related: #24104

[markjaquith]

Not going to do the separator permissions thing. I think that's better handled through #24104. We should clean up dupes and trailing/leading separators automatically.

[markjaquith]

In 24455:

Prevent an offset error if the first menu item is a separator.

props phill_brown. fixes #23182

[SergeyBiryukov]

#18327 was marked as a duplicate.